WO2010055865A1

WO2010055865A1 - Recording layer for optical information recording medium, optical information recording medium, and sputtering target

Info

Publication number: WO2010055865A1
Application number: PCT/JP2009/069222
Authority: WO
Inventors: 田内　裕基; 陽子志田
Original assignee: 株式会社神戸製鋼所
Priority date: 2008-11-12
Filing date: 2009-11-11
Publication date: 2010-05-20

Abstract

A recording layer for an optical information recording medium, which has a high reflectance (initial reflectance) and excellent recording characteristics; an optical information recording medium comprising the recording layer; and a sputtering target useful for forming the recording layer. The recording layer for an optical information recording medium, on which recording is performed by irradiation of laser light, is characterized by containing indium (In) oxide and palladium (Pd) oxide which includes palladium monoxide and palladium dioxide. The recording layer for an optical information recording medium is also characterized in that the ratio of Pd atoms contained in the recording layer relative to the total of In atoms and Pd atoms contained therein is 6-60 atom%.

Description

Recording layer for optical information recording medium, optical information recording medium, and sputtering target

The present invention relates to a recording layer for an optical information recording medium, an optical information recording medium, and a sputtering target useful for forming the recording layer.

Optical information recording media (optical discs) are typified by optical discs such as CDs, DVDs, and BDs, and are roughly classified into three types according to the recording / reproducing method: read-only type, write once type, and rewritable type. Of these, the write-once type optical disc recording method mainly includes a phase change method for changing the phase of the recording layer, an interlayer reaction method for reacting a plurality of recording layers, a method for decomposing a compound constituting the recording layer, and a hole in the recording layer. It is roughly classified into a drilling method in which recording marks such as pits are locally formed.

In the phase change method, a material using a change in optical characteristics due to crystallization of the recording layer has been proposed as a material for the recording layer. For example, Patent Document 1 proposes a recording layer containing Te—OM (where M is at least one element selected from a metal element, a metalloid element, and a semiconductor element), and Patent Document 2 proposes a recording layer containing Sb and Te. Layers have been proposed.

As the recording layer of the interlayer reaction type optical information recording medium, for example, in Patent Document 3, the first recording layer is made of an alloy containing In—O— (Ni, Mn, Mo), and the second recording layer is used. Has been proposed that is made of an alloy containing Se and / or Te element, O (oxygen), and one element selected from Ti, Pd, and Zr. Further, in Patent Document 4, a first recording layer: a metal containing In as a main component, and a second recording layer: a metal other than an oxide or a nonmetal containing at least one element belonging to Group 5B or Group 6B are stacked. Thus, it has been proposed to perform recording by reaction or alloying by heating.

As a recording layer of a method for decomposing a compound constituting the recording layer, for example, Patent Document 5 shows a recording layer mainly composed of nitride, and recording can be performed by decomposing the nitride by heating. Materials to be performed and organic pigment materials are being studied.

As the perforated recording layer, a recording layer made of a low melting point metal material has been studied. For example, Patent Document 6 proposes an alloy formed by adding an element of 3B group, 4B group, or 5B group to an Sn alloy, and the applicant of the present application also disclosed 1 to 50 atoms of Ni and / or Co in Patent Document 7. %, A recording layer made of an Sn-based alloy is proposed. In addition, the applicant of the present application disclosed in Patent Document 8 that an In alloy containing 20 to 65 atomic percent of Co, and an In alloy containing 19 atomic percent or less of one or more elements selected from Sn, Bi, Ge, and Si. A recording layer consisting of

Japanese Unexamined Patent Publication No. 2005-135568 Japanese Unexamined Patent Publication No. 2003-331461 Japanese Unexamined Patent Publication No. 2003-326848 Japanese Patent No. 3499724 International Publication No. 2003/101750 Pamphlet Japanese Unexamined Patent Publication No. 2002-225433 Japanese Unexamined Patent Publication No. 2007-196683 Japanese Patent No. 4110194

The required characteristics required for optical information recording media are mainly that it has sufficient reflectivity for reproduction, recording with practical recording laser power (high recording sensitivity), and recording signal for reproduction. It is required to have sufficient signal amplitude (high modulation degree) and high signal strength (high C / N ratio).

However, it is difficult for the recording material disclosed as the prior art to satisfy all of the required characteristics with the recording material alone. In the phase change method, since the reflectance of the recording layer alone is low, the reflection in the optical disk state is difficult. In order to increase the rate, a reflective film is required, and in order to increase the degree of modulation, it is necessary to provide dielectric layers such as ZnS—SiO 2 に above and below the recording layer, and the number of layers constituting the optical disk increases. In addition, since the interlayer reaction method also requires a plurality of recording layers, the number of layers constituting the optical disk increases. For this reason, there is a problem that the number of film layers increases and productivity decreases. On the other hand, the perforation method has a high reflectivity of the recording layer itself and can secure a large degree of modulation, so that the number of layers constituting the optical disk can be reduced, but in achieving higher recording sensitivity, It turns out that further study is needed. Furthermore, durability of the recording layer (particularly durability against high temperature and high humidity) is also required.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide optical information capable of increasing the productivity of an optical information recording medium by satisfying the above required characteristics while reducing the number of layers of an optical disk. The object is to provide a recording layer for a recording medium, an optical information recording medium provided with the recording layer, and a sputtering target useful for forming the recording layer.

The gist of the present invention is shown below.
(1) A recording layer for an optical information recording medium on which recording is performed by laser light irradiation,
The recording layer contains In oxide and Pd oxide, the oxide Pd contains Pd monoxide and Pd dioxide, and the ratio of Pd atoms to the total of In atoms and Pd atoms contained in the recording layer is A recording layer for an optical information recording medium of 6 to 60 atomic%.
(2) The recording layer for optical information recording media according to (1), wherein the ratio of Pd dioxide to the total of Pd monoxide and Pd is 5 to 70 mol%.
(3) The recording layer for optical information recording media according to (1) or (2), wherein the film thickness is 5 to 100 nm.
(4) The recording layer for an optical information recording medium according to any one of (1) to (3), wherein recording is performed by generating bubbles in a portion irradiated with laser light.
(5) An optical information recording medium comprising the optical information recording medium recording layer according to any one of (1) to (4).
(6) An optical information recording medium comprising a recording layer on which recording is performed by laser light irradiation, and a dielectric layer formed adjacent to the recording layer,
The recording layer contains In oxide and Pd oxide, the oxide Pd contains Pd monoxide and Pd dioxide, and the ratio of Pd atoms to the total of In atoms and Pd atoms contained in the recording layer is 6 An optical information recording medium of ˜60 atomic%.
(7) The optical information recording medium according to (6), wherein the ratio of Pd dioxide to the total of Pd monoxide and Pd contained in the recording layer is 5 to 70 mol%.
(8) The optical information recording medium according to (6) or (7), wherein the dielectric layer includes an oxide, a nitride, a sulfide, a carbide, or a mixture thereof.
(9) The oxide contained in the dielectric layer is selected from the group consisting of In, Zn, Sn, Al, Si, Ge, Ti, Ta, Nb, Hf, Zr, Cr, Bi, and Mg 1 An oxide of at least one element, the nitride is at least one nitride of Si and Ge, the sulfide is Zn sulfide, and the carbide is selected from the group consisting of Si, Ti and W The optical information recording medium according to (8), which is a carbide of one or more elements.
(10) The optical information recording medium according to any one of (6) to (9), wherein the dielectric layer has a thickness of 2 to 40 nm.
(11) The optical information recording medium according to any one of (6) to (10), wherein the recording layer has a thickness of 5 to 100 nm.
(12) The optical information recording medium according to any one of (6) to (11), wherein recording is performed by generating bubbles in a portion irradiated with laser light in the recording layer.
(13) A sputtering target for forming the recording layer for an optical information recording medium according to any one of (1) to (4),
It contains In oxide and Pd (preferably mainly containing In oxide and Pd), and the ratio of Pd atoms to the total of In atoms and Pd atoms contained in the sputtering target is 6 to 60 atomic% (preferably 6 to 50%). Sputtering target that is atomic%).
(14) A sputtering target for forming a recording layer for an optical information recording medium according to any one of (1) to (4),
A sputtering target consisting essentially of an In-based alloy containing 6 to 60 atomic% (preferably 6 to 50 atomic%) of Pd in a ratio of Pd atoms to the total of In atoms and Pd atoms.
In the recording layer for optical information recording medium of (4) above, recording is performed by generating bubbles in the portion irradiated with the laser beam and changing the volume, (1) to (3) The recording layer for an optical information recording medium is preferable.
(8) The optical information recording medium according to (6) or (7), wherein the dielectric layer is made of an oxide, nitride, sulfide, carbide, or a mixture thereof. Is preferred.
The optical information recording medium of (9) above constitutes the dielectric layer, and the oxide is In, Zn, Sn, Al, Si, Ge, Ti, Ta, Nb, Hf, Zr, Cr, Bi, and Mg. An oxide of at least one element selected from the group consisting of: the nitride is at least one nitride of Si and Ge; the sulfide is Zn sulfide; and the carbide is Si, Ti. And the optical information recording medium according to (8), which is a carbide of one or more elements selected from the group consisting of W and W.
In the optical information recording medium of (12), recording is performed by generating bubbles in the portion of the recording layer irradiated with laser light and changing the volume thereof. The optical information recording medium is preferable.
The sputtering target (14) is a sputtering target for forming the recording layer for an optical information recording medium according to any one of (1) to (4), wherein Pd atoms relative to the sum of In atoms and Pd atoms A sputtering target made of an In-based alloy containing 6 to 60 atomic% (preferably 6 to 50 atomic%) of Pd is preferable.

According to the present invention, a recording layer for a write once optical information recording medium having a high reflectance (initial reflectance) and excellent recording sensitivity at a practical recording laser power, and the recording layer are provided. A write-once optical information recording medium having excellent layer durability can be provided. Moreover, according to the present invention, a sputtering target useful for forming the recording layer can be provided.

In the present specification, “excellent recording sensitivity” means a high C / N ratio (carrier-to-noise ratio, a signal at the time of reading) with a relatively low recording laser power, as will be described in detail in the section of the embodiment described later. This means that the ratio of the background noise output level) and a high degree of modulation can be realized.

3 is a TEM observation photograph of the surface of the recording layer for an optical information recording medium according to the present invention. It is a Pd state analysis result (Pd 3d5 / 2 photoelectron spectrum) in Examples.

The present inventors comprise a recording layer for a write once optical information recording medium having a higher reflectance than a conventional recording layer and excellent recording sensitivity at a practical recording laser power, and the recording layer. Intensive research was conducted to realize an optical information recording medium with excellent durability of the recording layer. As a result, unlike the conventional recording layer, if the recording layer contains In oxide and Pd and the oxidation Pd contains Pd monoxide and Pd, the oxidation layer is irradiated when the recording layer is irradiated with laser. Pd is heated by laser irradiation, decomposes and releases oxygen to change the structure of the recording layer. Specifically, a method of performing irreversible recording by generating bubbles in a portion irradiated with the laser, It has been found that the recording sensitivity can be remarkably increased as compared with the conventional case, and that the durability of the recording layer can be remarkably improved if the dielectric layer is formed adjacent to the recording layer.

The recording method using the recording layer is different from the phase change method using the fact that the structure of the recording layer before the laser irradiation is amorphous and is amorphous after the laser irradiation. .

The reason why the recording layer of the present invention is excellent in recording sensitivity is that the transmittance is increased (that is, the reflectance is decreased) in the portion where bubbles are generated by laser irradiation compared to the portion where bubbles are not generated. It is conceivable that the modulation degree could be increased.

Further, by containing oxidized Pd as described above, the refractive index can be increased as compared with the case where oxidized Pd is not included, and a high reflectance can be obtained. Further, since the light absorption rate of the film can be increased, the energy of the laser for signal recording can be efficiently changed to heat, and as a result, the decomposition of the oxidized Pd can be performed with a practical recording laser power. Is promoted, and the recording sensitivity can be sufficiently improved.

In order to fully exhibit these effects, the ratio of Pd atoms to the total of In atoms and Pd atoms contained in the recording layer (hereinafter sometimes referred to as “Pd amount”) needs to be 6 atomic% or more. If the amount of Pd is less than 6 atomic%, the amount of released oxygen is not sufficient because the amount of oxidized Pd that decomposes during laser irradiation is small, resulting in fewer bubbles, resulting in a lower signal intensity (C / N ratio). . Further, since the light absorption rate of the recording layer is also reduced, the laser power required for recording is increased, which is not preferable. The amount of Pd is preferably 8 atomic% or more, more preferably 10 atomic% or more.

On the other hand, when the amount of Pd exceeds 60 atomic%, the degree of modulation becomes small. Therefore, in the present invention, the upper limit of the amount of Pd is set to 60 atomic%. The upper limit of the amount of Pd is preferably 50 atomic%, more preferably 45 atomic%.

If the oxidized Pd contains, in particular, Pd monoxide and Pd dioxide, the recording sensitivity can be improved sufficiently. The reason is that Pd dioxide, which is more unstable than monoxide Pd, is easily decomposed by laser irradiation to release oxygen, and Pd dioxide is present in the monoxide Pd that is more stable than Pd dioxide. Thus, it is conceivable that the natural decomposition of Pd dioxide is suppressed and a stable recording layer can be obtained.

In order to increase the amount of oxygen released by the decomposition of the Pd dioxide and improve the recording sensitivity more sufficiently, the ratio of the Pd dioxide to the total of the Pd monoxide and the Pd dioxide is preferably 5 mol% or more. On the other hand, if there is too much Pd dioxide relative to Pd monoxide, Pd dioxide cannot exist stably and it may be difficult to produce a recording layer. The ratio of Pd dioxide is preferably 70 mol% or less. More preferably, it is 60 mol% or less.

The recording layer of the present invention includes an oxide of “In” in which the absolute value of the standard free energy of formation of oxide with respect to 1 mol of oxygen is larger than Pd together with the above-described oxide Pd. In this way, by containing In oxide, which is more stable than oxidized Pd, together with oxidized Pd, the change in form due to oxygen release when the oxidized Pd is decomposed can be made clear and large, and the recording sensitivity can be improved sufficiently. Can be made.

As described above, the recording layer of the present invention contains In oxide, and preferably contains 50 mol% or more of In oxide. The recording layer of the present invention may contain unavoidable impurities in addition to the oxidized In and oxidized Pd. In addition, Sn, Al, Bi, Cu, Nb, Ti, Si, and Ta are contained within a total amount of about 30 atomic% or less in the state of oxide or metal for the purpose of improving the absorptance and controlling the refractive index. You may go out.

The thickness of the recording layer depends on the structure of the optical information recording medium, such as inserting other layers such as a metal compound layer and a metal layer above and below the recording layer, but when the recording layer is used as a single layer (dielectric) Whether the body layer or the optical adjustment layer is not provided) or not, the thickness of the recording layer is preferably 5 to 100 nm. When the film thickness of the recording layer is smaller than 5 nm, there is a tendency that a sufficient change in reflectance due to recording is difficult to obtain. More preferably, it is 10 nm or more, More preferably, it is 20 nm or more, Most preferably, it is 25 nm or more. On the other hand, if the film thickness of the recording layer is larger than 100 nm, it takes time to form the film, the productivity is lowered, and the laser power required for recording tends to increase. More preferably, it is 70 nm or less, More preferably, it is 60 nm or less.

As described above, the recording layer of the present invention contains oxidized Pd (for example, PdO, PdO 2, PdOX, etc.). In order to obtain such a recording layer, the recording layer can be formed by sputtering. preferable. The sputtering method is preferable because the film thickness distribution uniformity within the disk surface can be secured.

In order to form the recording layer containing the oxidized Pd by sputtering, it is preferable that the ratio of the oxygen flow rate to the Ar (argon) flow rate is 0.5 to 10.0 as sputtering conditions. Other conditions in the sputtering method are not particularly limited, and a widely used method can be adopted. The gas pressure is in the range of 0.1 to 1.0 Pa, for example, and the sputtering power is in the range of 0.5 to 20 W / cm ² , for example. What is necessary is just to control to a range.

As a sputtering target (hereinafter, simply referred to as “target”) used in the sputtering method,
(A) Indium oxide (specifically, for example, containing 50 mol% or more of oxidized In) and Pd (eg, oxidized Pd and / or metal Pd), and with respect to the sum of In atoms and Pd atoms contained in the sputtering target A sputtering target characterized in that the ratio of Pd atoms is 6 to 60 atomic%,
(B) A sputtering target having a feature in that it is made of an In-based alloy containing 6 to 60 atomic% of Pd (for example, metal Pd) in the ratio of Pd atoms to the total of In atoms and Pd atoms can be mentioned. Also,
(C) A metal In target (pure In metal target) and a metal Pd target (pure Pd metal target) are used, and these are simultaneously discharged to perform multi-source sputtering.

In addition, as the sputtering target of the above (A), in particular, it is possible to use a product obtained by mixing and sintering powders of oxidized In and metal Pd, and in-plane uniformity of productivity and composition of the formed thin film. It is preferable in terms of thickness control.

In the production of the sputtering target, inevitable impurities may be mixed in the sputtering target as impurities even in a small amount. However, the component composition of the sputtering target of the present invention does not prescribe even the trace components that are inevitably mixed, and the trace amounts of these unavoidable impurities are allowed as long as the above characteristics of the present invention are not impaired.

The optical information recording medium of the present invention is characterized in that the recording layer is provided. The configuration other than the recording layer is not particularly limited, and a configuration known in the field of optical information recording media is adopted. It is also possible to provide the recording layer and the following dielectric layer formed adjacent to the recording layer.

The optical information recording medium of the present invention has a recording layer exhibiting the above excellent characteristics, but it is also necessary to maintain the above excellent characteristics even in a high temperature and high humidity environment, that is, to ensure excellent durability. It is. Under the above environment, the oxidized Pd in the portion not irradiated with laser (that is, recording is not performed) is gradually reduced to release oxygen, resulting in a change in optical characteristics and a decrease in reflectance. Appearance is considered as a cause of the decrease in durability. However, it seems that by forming the dielectric layer adjacent to the recording layer, unnecessary decomposition of oxidized Pd (particularly Pd dioxide) in the recording layer can be suppressed and stably held.

The above-mentioned “formation of the dielectric layer adjacent to the recording layer” includes, for example, the case where the dielectric layer is formed between the substrate and the recording layer and adjacent to the recording layer, and / or the recording layer and will be described later. A case where it is formed between the light transmission layer and adjacent to the recording layer can be mentioned.

The dielectric layer also improves durability by acting as an oxygen barrier layer. By preventing the escape of oxygen that can be caused by unnecessary decomposition of the oxidized Pd, it is possible to prevent a change in reflectance (particularly, a decrease in reflectance), and to secure the reflectance necessary for the recording layer.

Further, recording characteristics can be improved by forming a dielectric layer. This is because the thermal diffusion of the laser incident by the dielectric layer is optimally controlled to prevent the bubbles in the recording portion from becoming too large or the decomposition of the oxidized Pd from proceeding too much to collapse the bubbles. This is considered to be possible to optimize.

Examples of the material of the dielectric layer include oxides, nitrides, sulfides, carbides, fluorides, or mixtures thereof. Examples of the oxides include In, Zn, Sn, Al, Si, Ge, Ti, and Ta. And oxides of one or more elements selected from the group consisting of Nb, Hf, Zr, Cr, Bi, and Mg. The nitride is a nitride of one or more elements selected from the group consisting of In, Sn, Ge, Cr, Si, Al, Nb, Mo, Ti, and Zn (preferably Si and / or Ge nitridation). And sulfides include Zn sulfide. The carbide is a carbide of one or more elements selected from the group consisting of In, Sn, Ge, Cr, Si, Al, Ti, Zr, Ta and W (preferably from the group consisting of Si, Ti and W). The carbide of one or more elements selected) and the fluoride include a fluoride of one or more elements selected from the group consisting of Si, Al, Mg, Ca, and La. Examples of such a mixture include ZnS—SiO2. Of these, more preferable is the above compound (oxide or the like) containing at least one of In, Zn, Sn, Al, Si, Ti, and Mg, or a mixture thereof, and more preferable is In, Zn, Sn, The above-mentioned compound containing any one or more elements of Al or a mixture thereof.

The film thickness of the dielectric layer is preferably 2 to 40 nm. This is because if the thickness is less than 2 nm, the effect of the dielectric layer (particularly, the effect as an oxygen barrier) is hardly exhibited. More preferably, it is 3 nm or more. On the other hand, if the dielectric layer is too thick, it is difficult for the recording layer to change (generate bubbles) due to laser irradiation, and the recording characteristics may be deteriorated. Therefore, the thickness of the dielectric layer is preferably 40 nm or less, more preferably 35 nm or less.

The present invention does not define the method for forming the dielectric layer, but it is preferable to form the dielectric layer by the sputtering method as in the recording layer.

In forming the dielectric layer by sputtering, the sputtering conditions are Ar flow rate, for example, in the range of 10 to 100 sccm, and when using a metal target as described below, the oxygen flow rate during oxide layer formation is For example, the range is 5 to 60 sccm, and the nitrogen flow rate when forming the nitride layer is, for example, 5 to 80 sccm. Further, for example, the gas pressure may be in the range of 0.1 to 1.0 Pa, and the sputtering power may be in the range of 0.5 to 50 W / cm 2, for example.

As a sputtering target used for forming the dielectric layer, in addition to a target made of the above compound (oxide, nitride, sulfide, carbide, fluoride), other than oxygen, nitrogen, sulfur, carbon, fluorine in the compound A metal target containing a constituent element (a target made of a pure metal or an alloy) can be used.

In the optical information recording medium of the present invention, the configuration other than the recording layer and the dielectric layer is not particularly limited, and a configuration known in the field of optical information recording media can be adopted.

As an optical information recording medium (optical disk), a structure in which a recording layer is laminated on a substrate in which a laser guide groove is engraved, and a light transmission layer is further laminated on the substrate.

For example, examples of the material of the substrate include polycarbonate resin, norbornene resin, cyclic olefin copolymer, and amorphous polyolefin. Further, as the light transmission layer, polycarbonate or ultraviolet curable resin can be used. As a material for the light transmission layer, it is preferable that the light transmission layer has a high transmittance with respect to a laser for recording and reproduction, and has a small light absorption rate. The thickness of the substrate is, for example, 0.5 mm to 1.2 mm. In addition, the thickness of the light transmission layer is, for example, 0.1 mm to 1.2 mm.

The recording layer of the present invention exhibits high reflectivity and exhibits excellent recording characteristics by itself. However, if necessary, the recording layer may be above and / or below the recording layer to improve the durability of the recording layer. In addition, an oxide layer, a sulfide layer, a metal layer, or the like may be provided. By laminating these layers, it is possible to suppress oxidation and decomposition, which are deterioration with time of the recording layer. Further, an optical adjustment layer or a dielectric layer may be provided between the substrate and the recording layer in order to further increase the reflectivity of the optical disk. Examples of the material of the optical adjustment layer include Ag, Au, Cu, Al, Ni, Cr, Ti, and alloys thereof.

In the above, a single-layer optical disc in which one recording layer and one light transmission layer are formed is shown. However, the present invention is not limited to this, and two or more optical discs in which a plurality of recording layers and light transmission layers are stacked are shown. It may be.

In the case of the two or more optical discs, for example, an ultraviolet curable resin or a polycarbonate between a recording layer group consisting of a recording layer and an optical adjustment layer or a dielectric layer laminated as necessary, and another recording layer group A transparent intermediate layer made of a transparent resin or the like may be included.

A feature of the present invention is that the recording layer described above is employed. In this case, a method for forming a substrate other than the recording layer, a light transmission layer, an optical adjustment layer, a dielectric layer, a transparent intermediate layer, etc. The optical information recording medium may be manufactured by being formed by a usual method without being particularly limited.

The present invention is also characterized in that the recording layer described above is employed and a dielectric layer is formed adjacent to the recording layer. In this case, a substrate other than the recording layer and the dielectric layer and light transmission There is no particular limitation on the method of forming the layer, and further, the optical adjustment layer, the transparent intermediate layer, etc., and the optical information recording medium may be produced by forming it by a conventional method.

Examples of the optical information recording medium include CD, DVD, and BD. For example, a BD capable of recording and reproducing data by irradiating a recording layer with blue laser light having a wavelength of about 380 nm to 450 nm, preferably about 405 nm. A specific example is -R.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the following examples are not intended to limit the present invention, and may be implemented with appropriate modifications without departing from the spirit of the preceding and following descriptions. And are within the scope of the present invention.

(Experimental example 1)
(1) Production of optical disk A polycarbonate substrate (thickness: 1.1 mm, diameter: 120 mm, track pitch: 0.32 μm, groove depth: 25 nm) was used as a disk substrate, and a DC magnetron sputtering method was used on the substrate. As shown in Table 1, recording layers having various amounts of Pd were formed. The film thickness of the recording layer was 40 nm. Sputtering was performed by simultaneously discharging a pure In metal target and a pure Pd metal target.

The sputtering conditions for forming the recording layer were Ar flow rate: 10 sccm, oxygen flow rate: 10 sccm, gas pressure: 0.4 Pa, DC sputtering power: 100 to 200 W, and substrate temperature: room temperature. The component composition (Pd amount) of the formed recording layer was measured by ICP emission analysis, fluorescent X-ray analysis, or X-ray photoelectron spectroscopy.

In addition, No. in Table 1 below. For No. 5, the ratio of Pd contained in the recording layer to the metal Pd and oxidized Pd (Pd atomic ratio) was determined. Specifically, a depth direction analysis was performed using an X-ray photoelectron spectrometer Quantera SXM manufactured by Physical-Electronics. From the area intensity ratio of the peaks of the metal Pd and the oxidized Pd at the center of the film, the metal Pd and the oxidized Pd The above ratio was determined. As a result, no. The ratio of metal Pd to oxide Pd in No. 5 was 69:31.

In was present in the formed recording layer as an oxide.

Next, an ultraviolet curable resin (“BRD-864” manufactured by Nippon Kayaku Co., Ltd.) was spin-coated on the recording layer obtained as described above, and then irradiated with ultraviolet rays to have a film thickness of about 0.1 mm. A light transmission layer was formed to obtain an optical disk.

(2) Evaluation of optical disc The (initial) reflectance and recording characteristics of the produced optical disc were evaluated as follows.

With an optical disk evaluation device ("ODU-1000" manufactured by Pulstec Industrial Co., Ltd., recording laser wavelength: 405 nm, NA (numerical aperture): 0.85), the laser is irradiated onto the track and converted from the return intensity of the reflected light. Thus, the reflectance at a wavelength of 405 nm was determined.

Using the above optical disk evaluation apparatus, recording laser power (recording power): in the range of 2 mW to 20 mW, linear velocity: 4.92 m / s, length: 0.60 μm, recording mark (Blu-ray Disc 8T signal) Was repeatedly formed.

Then, using a spectrum analyzer (“R3131R” manufactured by Advantest Corporation), the signal intensity of the 4.12 MHz frequency component at the time of signal reading at a reproduction laser power of 0.3 mW: carrier C (unit dB) and the signal of the frequency component before and after that Intensity: A ratio (C / N ratio, unit dB) to noise N (unit dB) was measured. Then, the highest C / N ratio and the recording laser power when the highest C / N ratio was obtained were obtained.

The degree of modulation was calculated from the following formula (1) by determining the reflectance of the unrecorded portion and the reflectance of the recorded portion.
Modulation degree (change rate of reflectance) = (reflectance of unrecorded portion−reflectance of recorded portion) / (reflectance of unrecorded portion) (1)

These results are also shown in Table 1. The reflectance is 4% or more, the recording power (recording laser power when the highest C / N ratio is obtained) is 9 mW or less, and the C / N ratio (the highest C / N ratio) is 45 dB or more. In addition, those having a modulation degree of 0.40 or more were evaluated as having high reflectivity (initial reflectivity) and excellent recording sensitivity with practical recording laser power.

From Table 1, it can be considered as follows. That is, it can be seen that the recording layer satisfying the definition of the present invention has a high reflectance and a high recording sensitivity even when the recording laser power is low.

On the other hand, when the amount of Pd falls below the lower limit defined in the present invention, it can be seen that the degree of modulation is small and the recording sensitivity is low. It can also be seen that the recording layer itself has a low reflectance, and a higher recording power is required.

Also, it can be seen that when the amount of Pd exceeds the upper limit defined in the present invention, the modulation degree is remarkably lowered and the recording sensitivity is low.

(Experimental example 2)
An optical disc was produced and evaluated in the same manner as in Experimental Example 1 except that a recording layer having the component composition shown in Table 2 below was formed using pure Cu or pure Ag instead of pure Pd as a sputtering target. The results are shown in Table 2.

From Table 2, when only Ag or Cu was contained instead of Pd, there were problems such as low reflectivity, low C / N ratio, or insufficient modulation.

(Experimental example 3)
Except for changing the film forming gas flow rate during film formation as shown in Table 3 below, in the same manner as in Experimental Example 1, No. 1 in Table 3 was obtained. 2 optical disks were prepared and evaluated. The results are shown in Table 3. In Table 3, No. 1 is No. 1 in Table 1. Same as 5.

Table 3 shows that the amount of oxygen contained in the recording layer is small and In and Pd are not sufficiently oxidized (No. 2), and the amount of oxygen contained in the recording layer is No. 2. No. 2 more than 2. No. 1 is compared with each other when recording is performed with the same recording power. In case of 2, there was a problem that a sufficient C / N ratio and modulation degree could not be obtained.

Incidentally, a TEM observation photograph of the surface of the recording layer after laser irradiation was taken with respect to those having good recording characteristics satisfying the provisions of the present invention. The TEM observation photograph is shown in FIG. As shown in FIG. 1 (particularly, enlarged photograph), those satisfying the provisions of the present invention have sufficient recording sensitivity because, as described above, the oxidized Pd in the recording layer decomposes to generate oxygen and bubbles are generated. It seems to have been raised.

(Experimental example 4)
(1) Production of optical disk A polycarbonate substrate (thickness: 1.1 mm, diameter: 120 mm, track pitch: 0.32 μm, groove depth: 25 nm) was used as a disk substrate, and a DC magnetron sputtering method was used on the substrate. Recording layers having various contents of In oxide, metal Pd, and oxide Pd (the molar ratio of Pd monoxide and Pd in the total of Pd monoxide and Pd dioxide is as shown in Table 4) did. The film thickness of the recording layer was 40 nm. Sputtering was performed by multi-source sputtering by simultaneous discharge of two targets, a pure In metal target and a pure Pd metal target. The sputtering conditions for forming the recording layer were constant at Ar flow rate: 10 sccm, and the oxygen flow rate introduced simultaneously with Ar was changed within the range of 5 to 50 sccm as shown in Table 4. The gas pressure was 0.4 Pa, the DC sputtering power was 100 to 200 W, and the substrate temperature was room temperature.

The component composition (Pd amount) of the formed recording layer was measured by ICP emission analysis, fluorescent X-ray analysis, or X-ray photoelectron spectroscopy.

Next, an ultraviolet curable resin (“BRD-864” manufactured by Nippon Kayaku Co., Ltd.) is spin-coated on the obtained recording layer, and then irradiated with ultraviolet rays to form a light transmission layer having a thickness of about 0.1 mm. Film was obtained to obtain an optical disk.

The state analysis of Pd was performed as follows. That is, the outermost surface spectrum of the recording layer is measured by X-ray photoelectron spectroscopy (the apparatus is a Quanta SXM manufactured by Physical Electronics Co., Ltd.), and the peak separation of the Pd 3d5 / 2 photoelectron spectrum is performed. Presence form of Pd present in: The molar ratio (mol%) of metal Pd, monoxide Pd, and Pd dioxide was determined. The charge was corrected using photoelectrons from the C1s level as a reference. The analysis was performed in a state where the light transmission layer (cover layer) of the optical disc was peeled off and a recording layer was formed on the polycarbonate substrate, and the analysis region was about φ200 μm. As an example of the spectrum, No. The Pd を 3d5 / 2 photoelectron spectrum of No. 4 is shown in FIG.

(2) Evaluation of optical disc The produced optical disc was evaluated as follows. That is, an optical disk evaluation apparatus (“ODU-1000” manufactured by Pulstec Industrial Co., Ltd.) was used, a recording laser center wavelength was set to 405 nm, and a lens with NA (numerical aperture): 0.85 was used. The reflectance shown below was obtained from the intensity of the return light of the laser beam in the unrecorded portion of the optical disk by irradiating the track with the laser using the above-mentioned apparatus.

Using the optical disk evaluation apparatus, random signals of 2T to 8T were recorded with various recording laser powers (recording powers) under conditions of a linear velocity of 4.92 m / s and a reference clock of 66 MHz. Then, the recording laser power (the value indicating the fluctuation on the time axis of the reproduction signal at the time of recording and reproduction at the reproduction laser power of 0.3 mW) measured using the Yokogawa time interval analyzer TA810 is minimized. (Recording power) was determined (values are as shown in Table 4), and the degree of modulation (change rate of reflectance) at the recording power at which the jitter value was minimized was determined from the following formula (1). And the thing whose this modulation degree is 0.40 or more was set as the pass.
Modulation degree (change rate of reflectance) = (reflectance of unrecorded portion−reflectance of recorded portion) / (reflectance of unrecorded portion) (1)

From Table 4, the degree of modulation is increased by the presence of Pd dioxide as the oxidized Pd, and in particular, the ratio of Pd dioxide to the total of Pd monoxide and Pd dioxide is within the recommended range. It can be seen that a high degree of modulation can be obtained. No. In No. 6, the recording power and the modulation degree could not be measured, but barely recorded, the recording power was 5.5 mW and the modulation degree was 0.15.

(Example 5)
(1) Production of optical disk A polycarbonate substrate (thickness: 1.1 mm, diameter: 120 mm, track pitch: 0.32 μm, groove depth: 25 nm) was used as a disk substrate. And in Table 5 below, No. For 3 to 5 and 9 to 12, a dielectric layer (lower) having the components and film thicknesses shown in Table 5 was formed by DC magnetron sputtering using an oxide target or a pure metal target. The sputtering conditions for forming this dielectric layer (lower) are: Ar flow rate: 10-30 sccm, oxygen flow rate (when using a pure metal target as a target): 0-10 sccm, gas pressure: 0.2-0.4 Pa, DC sputtering power: 100 to 400 W, substrate temperature: room temperature.

Next, a recording layer was formed. In detail, on the substrate [No. For 3 to 5 and 9 to 12, recording layers having a ratio of In atoms to Pd atoms of 60:40 were formed on the dielectric layer (lower) by a DC magnetron sputtering method. The film thickness of the recording layer was 40 nm. Sputtering was performed by multi-source sputtering by simultaneous discharge of two targets, a pure In metal target and a pure Pd metal target. The sputtering conditions for forming the recording layer were Ar flow rate: 10 sccm, oxygen flow rate: 15 sccm, gas pressure: 0.4 Pa, DC sputtering power: 100 to 200 W, and substrate temperature: room temperature.

Next, no. For 2 to 12, an oxide target or a pure metal target (for example, ZnS—SiO 2 metal, metal Mg, metal Zn, metal Sn, metal Bi, metal Ti, etc. as a target) is used in the same manner as the above dielectric layer (lower). A dielectric layer (upper) having the components and film thicknesses shown in Table 5 was formed.

Next, No. No. 1 on the recording layer and No. 1 For 2 to 12, an ultraviolet curable resin (“BRD-864” manufactured by Nippon Kayaku Co., Ltd.) is spin-coated on the dielectric layer (top), and then irradiated with ultraviolet rays to transmit light having a thickness of about 0.1 mm. A layer was formed to obtain an optical disk.

The recording layer contains oxidized In and oxidized Pd, and the oxidized Pd contains oxidized Pd and oxidized Pd. The ratio of oxidized Pd to the total of oxidized Pd and oxidized Pd is 27.8. It was confirmed separately that it was mol%. The Pd state analysis was performed as follows. That is, the outermost surface spectrum of the recording layer was measured by X-ray photoelectron spectroscopy (the apparatus was Quantera SXM manufactured by Physical Electronics), and the peak separation of the Pd 3d5 / 2 photoelectron spectrum was performed. Presence form of Pd present in: The molar ratio (mol%) of metal Pd, monoxide Pd, and Pd dioxide was determined. The charge was corrected using photoelectrons from the C1s level as a reference. The analysis area was about φ200 μm.

(2) Evaluation of optical disk The durability of the manufactured optical disk was evaluated as follows.

With an optical disk evaluation apparatus (“ODU-1000” manufactured by Pulstec Industrial Co., Ltd., recording laser wavelength: 405 nm, NA (numerical aperture): 0.85), the laser is irradiated onto the track, and the laser beam of the unrecorded portion of the optical disk The reflectance (initial reflectance) at a wavelength of 405 nm was determined in terms of the return light intensity.

In addition, an accelerated environment test (constant temperature and humidity test) was held for 96 hours in an air atmosphere at a temperature of 80 ° C. and a relative humidity of 85%, and the reflectance after the test was measured in the same manner as described above. And the change rate of the reflectance was calculated | required from following formula (2). These results are also shown in Table 5.
Rate of change in reflectance (%) = 100 × (reflectance after test [%] − initial reflectance [%]) / initial reflectance [%] (2)

From Table 5, by forming the dielectric layer adjacent to the recording layer, the change in reflectance can be made sufficiently smaller than when the dielectric layer is not formed, and an optical information recording medium excellent in durability can be obtained. It can be seen that it can be realized. In particular, it can be seen that by forming the dielectric layer above and below the recording layer, the rate of change in reflectivity is remarkably reduced and the durability is excellent.

Although this application has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application includes Japanese patent applications filed on November 12, 2008 (Japanese Patent Application No. 2008-290309), Japanese patent applications filed on September 18, 2009 (Japanese Patent Application No. 2009-217291), and applications filed on September 18, 2009. This is based on a Japanese patent application (Japanese Patent Application No. 2009-217292), the contents of which are incorporated herein by reference.

Claims

A recording layer for an optical information recording medium on which recording is performed by laser light irradiation,
The recording layer contains In oxide and Pd oxide, the oxide Pd contains Pd monoxide and Pd dioxide, and the ratio of Pd atoms to the total of In atoms and Pd atoms contained in the recording layer is A recording layer for an optical information recording medium of 6 to 60 atomic%.
The recording layer for an optical information recording medium according to claim 1, wherein the ratio of Pd dioxide to the total of Pd monoxide and Pd is 5 to 70 mol%.
The recording layer for an optical information recording medium according to claim 1, wherein the film thickness is 5 to 100 nm.
The recording layer for an optical information recording medium according to claim 1, wherein recording is performed by generating bubbles in a portion irradiated with laser light.
An optical information recording medium comprising the recording layer for an optical information recording medium according to any one of claims 1 to 4.
An optical information recording medium comprising a recording layer on which recording is performed by laser light irradiation, and a dielectric layer formed adjacent to the recording layer,
The recording layer contains In oxide and Pd oxide, the oxide Pd contains Pd monoxide and Pd dioxide, and the ratio of Pd atoms to the total of In atoms and Pd atoms contained in the recording layer is 6 An optical information recording medium of ˜60 atomic%.
The optical information recording medium according to claim 6, wherein the ratio of Pd dioxide to the total of Pd monoxide and Pd contained in the recording layer is 5 to 70 mol%.
The optical information recording medium according to claim 6, wherein the dielectric layer contains an oxide, a nitride, a sulfide, a carbide, or a mixture thereof.
The oxide contained in the dielectric layer is at least one selected from the group consisting of In, Zn, Sn, Al, Si, Ge, Ti, Ta, Nb, Hf, Zr, Cr, Bi, and Mg. An oxide of an element, the nitride is at least one nitride of Si and Ge, the sulfide is a Zn sulfide, and the carbide is one selected from the group consisting of Si, Ti, and W The optical information recording medium according to claim 8, which is a carbide of the above element.
The optical information recording medium according to claim 6, wherein the dielectric layer has a thickness of 2 to 40 nm.
The optical information recording medium according to claim 6, wherein the recording layer has a thickness of 5 to 100 nm.
The optical information recording medium according to claim 6, wherein recording is performed by generating bubbles in a portion of the recording layer irradiated with laser light.
A sputtering target for forming a recording layer for an optical information recording medium according to any one of claims 1 to 4,
A sputtering target containing In and Pd oxide, and the ratio of Pd atoms to the total of In atoms and Pd atoms contained in the sputtering target is 6 to 60 atomic%.
A sputtering target for forming a recording layer for an optical information recording medium according to any one of claims 1 to 4,
A sputtering target consisting essentially of an In-based alloy containing 6 to 60 atomic% of Pd in the ratio of Pd atoms to the sum of In atoms and Pd atoms.